Ferromagnetic materials



Patented Aug. 23, 1932 amino STATES PATENT OFFICE BEBNHABD SCHARNOW, OF IBERLIN-CEARLOTTENBURG, GERMANY, ASSIGNOB, TO DEUTSOH-ATLANTISCHE TELEGRAPHENGESELLSCEA-FT, OF BERLIN, GERMANY ra'nnomenn'ric surname 30 Drawing. =App1ication filed April 21, 1930, Serial No. 446,168, and in Germany December 10, 1928.

This invention relates to magnetic alloys of the nickel-iron class having a high permeability at low magnetizing forces such as used for loading telephone and tdlegraph 5 conductors or the like in electrical circuits.

It aims to increase the constancy of permeability in low magnetizing fields by increasing the small coercivity of such metals without unduly impairing the general high 19 order of initial permeability, so as to improve their character and applicability to the stated and other uses as will be better understood from the following description.

Chief among the properties required in al-.

loys of this kind are :((i) high initial per:

meability, and (b) a relatively small change I in permeability throughout the largest possible range of small field strengths. Condition (1)) is fulfilled by an alloy having a comparatively high coercivity, since 'it is well known that the higher the coercivity of alloys of a certain class becomes, the less the dependence of the permeability on the strength of field at small magnetizing forces.

In the following description therefore, the

amount of the coercivity will be taken as an inverse measure of the change of the perineability with strength of field.

It is well know that pure nickel-iron al- 0 loys, especially those having approximately 80% nickel content possess an extraordinarily high initial permeability, but these suffer a relatively great change of permeability with changing strength of field. Other alloys, such as those consisting for example of cobalt, iron and nickel, show an extraordi-' narily small increase of permeability with varied strength of field and-accordingly satisfy the above-mentioned condition (6).

However, with these last-mentioned alloys there is alimit to the magnitude of initial permeability, which limit renders the alloy unsuitable for many purposes.

5 The present invention provides a generally applicable method of procedure which, in the case of nickel-iron alloys of high initial permeability and small coercivity makes it possible to increase the coercivity and thereby to decrease the change-in-permeability, without unduly-lowering the value of t e initial permeability. It embodies a process in the manufacture or thermal production of alloys with finely distributed heterogeneous iron alloys should be completely in solid solution, and when additional elements have been proposed either to increase the initial permeability or the specific resistance, or else to render mechanical treatment easier, their nature and amount have been selected so as to bring about their complete solid solution. For example, manganese, chromium, cobalt, tungsten, copper, silicon, molybdenum and the like have been added to nickel-iron alloys in such proportions that all formed mixed crystals therewith.

The behavior of metals is of course known so far as the forming of mixed crystals, or solutions in each other is concerned. For

-. instance, it is known that an alloy of nickel and iron is capable of taking up a considerable percentage of copper in the mixed crys tals of nickel and iron. Only after a certain limit of copper addition is passed are parts of the copper found in the solid body as separate heterogeneous constituents. The conditions under which these constituents are formed have been known for many materials, although tests have not been made for all the different metals and alloys. However,

it was not known that heterogeneous constitu-' tion in nickel-iron alloys of high initial permeability might be used to achieve a special a technical effect and create, so to speak, an r inner tension causing an increase of'the coercivity of the metals.

The discovery of this from prior knowledge and practice, there are produced in the high initial permeability alloys certain materials or elements such as silver out of solid solution and disseminated fact led to this in- 'vention, according to which, as distinguished I in a finely divided state. A particular form I of heat treatment is required to produce the i desired result according .to the invention, which heat treatment comprises heating the alloy, after working it to shape as desired,- to an annealing temperature, e. g. 900. C. or

above, vthen quenching it from that temperature, or from a somewhat lower temperature, e. g. 600 0., in order to obtain a condition of super-saturation of the added element in solid solution, and thereafter soaking the ma-' terial at-a temperature such as 300 to 500 C. for a sufliciently long time.

The separate or heterogeneous particles left in the material (whether they be of micro scopic or sub-microscopicsize) then set up a state of strain therewithin owing to the difference of their thermal coefficients of eXpan-.

sion or to the occurrence of a change of volume, by which state of strain the coerclvity of the material is increased. The initial permeability however is affected only within certain limits. The value of the initial permeability and of the coercivity may be varied by varying the nature and'quantitv of the added substance as well as by. suitably varying the details of the heat treatment. and within limits any desired combination of both values can be obtained. v 4

The coeflicients of solubility of the individ-. ual substances with respect to each other are sufliciently known in science and engineering. Also if several substances are soluble in thereof. arsenic. beryllium. boron. phosphorus, sulphur and zirconium are other possibilities. It is therefore immaterial which of the well known materialsflor elements is added to "the metal or alloy so long as it has or shows, when used in comparatively small amounts, the special behavior of forming heterogeneous constituents which do not pass into or stay in solid solution at room temperature. Elements such as copper, which are comparatively soluble in the nickel-iron solid complex, cannot be usefully employed according to the present invention.

The following table shows the efi'ect of annealinga nickel-iron alloy with an addition of silver, coolingrapidly from 600 C.

I and shows thatthe coercitivity can be increased at will, while retaining a substantially high initial permeability:

Alloy 77.5% m, 20.5% i e/2.5% A

Initial Coerciv- State permeability Rapidly cooled from 600 C 5880 0. Aged (or 1 hour at 350 0..-- 4812 0. Aged for 6 hours at 350 C 4030 0. Aged for 11 hours at 350 C 4100 0. Aged for 16 hours at 350 0..-. 3630 0. Aged for 21 hours at 350 C 3570 0.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is 1. The process of producing magnetic alloys of the nickel-iron class with high in1t1al permeability and with reduced variation of permeability in small magnetic fields, char acterized by incorporating'in the alloy an additional element which does not readily form mixed crystals with the nickel-iron complex, heating the alloy and quenching it -from a high temperature so as to obtain a condition of super-saturation of the element in solid solution and thereafter soaking the material at a lower temperature for a substantial period of time, in order to precipitate some of the element out of solution in a finely divided state. 2. The process of producing magnetic alloys of the nickel-iron class with high initial permeability and with reduced variation of permeability in small magnetic fields, characterized by incorporating in the alloy an additional element which does not readily form mixed crystals with the nickel-iron complex, heating the alloy to an annealing temperature, quenching so as to obtain a condition of super-saturation of the element in solid solution, and thereafter soaking the ma terial between about 300 and 500 C. for a substantial period of time in order to precipitate some of the element out of solution in a finely divided state. I

3. The process of producing magnetic alloys of the nickel-iron class with high initial permeability and with reduced variation of permeability in small magnetic fields, characterized by incorporating in the alloy an additional element which does not readily form mixed crystals with the nickel-' iron complex, heating the alloy to an annealing temperature, cooling rather slowly to a lower temperature, such for example as 600 C., quenching so as to obtain a condition of super-saturation of the element in solid solution, and thereafter soaking the material between about 300 and 500 C. for a substantial period of time in order to precipitate some of the element out of solution in a finely divided state.

4. The process of producing magnetic alloys of the nickel-iron class with high initial permeabilityand with reduced variation of permeability in small magnetic fields, characterized by incorporating silver in the' alseminated in a finely divided state "through v 10y, heating the alloy and quenching it from I a high temperature so as to obtain a condition ofsuper-saturation of the silver in-solid solution, and thereafter soaking the'material 6 between about 300 and 500 C. for: a substantial period of time in order to precipitate silver out of solid solution in a finely divided.

- 5. The process l loys ofthe nickel-iron class with high initial permeability and with reduced variation of Permeability n Small magnetic fields, ch ,p Y

V acterized by incorporating silver in the alloy, heating to at least 900? (3., quenching in order 15 to obtain aconditionof super-saturationof Y the silver in solidsolution and thereaflien soaking-the material betweenabout350iand- 400 C. in orderto precipitate silv r'paciot, I solid solution 'in'a finely divided-state." v "6." The process of producing "magnetic a1! loys of the nickel-iron class with highfinitialf' I ample as 600 0., quenehing'irom-thatitem perature in order to obtain acondition of'su-q per-saturation of. the silverin solid solution, 1

8 and thereafter soaking the material between about 350*. and 400 o. in order to-precipitate' 1 a l r out of solid so1utioni afin 1 w state. a

7; Process as claimed in' claim 4; mm 4 the unt of silver incorporated about 0.3% and 5%; a

,8. Process as claimed inthe amount of 2.5%; m 9. Amagnetic havingra high initial permeability and relai-i t y small variation ofpermeflbilityi magnetic field, characterizedby comprising."

an additional element of a kind which does I not readily form, mixed crystals with the k nickel-iron complex, the element being out'of solid solution and disseminated-hm.

finely divided state-throughoutthe'mass at;

'the alloy.

" 10. A magnetic alloy 'ofthe nickel-iron} class having a high initial'permeabilit'y .-and-" j relatively smallvariation of permeability in small magnetic fields,'characteriz'ed by c0'ni'-.

, Prisin 'silver out of solid soluti b h mass of the alloy. 7 A magnetic lloyof;

.7. the ackei ii classhavmg a high initial permeability and relatively small'variationof permeabihty'inj m ll magneticfields, characterized. by v prising between 0.3% and 5% silver outl'of.

solid solution and. ated in. a finely gil'lvided throughout the (if-the I a -12QA magnetic ma the of producing ma gnetic a1- permeability andwith' reduced variationof permeability in small magnetic fields, {char-Iii;

acteri'zed by incorporating'silver inthealloyf' heating-teat .least 900 6;, rather 1 slowly to a lower temperature,,such forfex- 61am 4, n amen; 5 silver incorporated is about:

at of the-nickel iren @1555; F 3

class having'a'highcinitiah rmeability relatively. small'variationo perm bihty in small ma ,etiefields; b com: prising 'a ut2;5%fsilvcrj9utof 01 solui w i a and statethriouglioutthe mas's ofthe a 0y.

and

divided I Intestimon {whe'moflaflixm s1 stud; 

